JP5219745B2 - Light emitting device - Google Patents
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Classifications
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K50/00—Organic light-emitting devices
- H10K50/80—Constructional details
- H10K50/85—Arrangements for extracting light from the devices
- H10K50/856—Arrangements for extracting light from the devices comprising reflective means
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K50/00—Organic light-emitting devices
- H10K50/80—Constructional details
- H10K50/85—Arrangements for extracting light from the devices
- H10K50/858—Arrangements for extracting light from the devices comprising refractive means, e.g. lenses
Description
本発明は発光装置に関するものである。 The present invention relates to a light emitting device.
有機ＥＬ発光装置は、薄膜で自発光を特徴とした有機ＥＬ素子から構成され、新方式のフラットパネルディスプレイとして応用されている。有機ＥＬ素子は、陰極から電子を、陽極からホール（正孔）を有機層に注入し、有機層中の発光層で励起子を生成させ、これら励起子が基底状態にもどる際に光が放出される原理を利用している。発光層は、蛍光性有機化合物若しくは燐光性有機化合物、量子ドットなどの発光性材料からなる。 Organic EL light-emitting devices are composed of thin-film organic EL elements characterized by self-luminescence, and are applied as a new flat panel display. An organic EL device injects electrons from the cathode and holes (holes) from the anode into the organic layer, generates excitons in the light emitting layer in the organic layer, and emits light when these excitons return to the ground state. The principle is used. The light emitting layer is made of a light emitting material such as a fluorescent organic compound, a phosphorescent organic compound, or a quantum dot.
このような有機ＥＬ発光装置の開発課題の一つとして、発光効率の向上がある。有機ＥＬ素子の構成は、通常、陽極、発光層を含む有機層および陰極が１次元的に積層された構成である。このとき、空気の屈折率よりも発光層の屈折率（約１．７〜１．９程度）の方が大きい。このため、発光層の内部から放出された光の大部分は、高屈折率から低屈折率へ変化する積層膜の界面で全反射されて、基板に水平な方向に伝播する導波光となり、素子内部に閉じ込められることになる。発光層の内部で発生した光のうち外部に取り出して利用できる光の割合（光取り出し効率）は、通常、約２０％程度でしかない。 One of the development issues of such an organic EL light emitting device is to improve luminous efficiency. The configuration of the organic EL element is usually a configuration in which an anode, an organic layer including a light emitting layer, and a cathode are laminated one-dimensionally. At this time, the refractive index of the light emitting layer (about 1.7 to 1.9) is larger than the refractive index of air. For this reason, most of the light emitted from the inside of the light emitting layer is totally reflected at the interface of the laminated film that changes from a high refractive index to a low refractive index, and becomes guided light that propagates in a direction horizontal to the substrate. It will be trapped inside. Of the light generated inside the light emitting layer, the proportion of light that can be extracted and used outside (light extraction efficiency) is usually only about 20%.
よって、有機ＥＬ発光装置の発光効率を改善するためには、この光取り出し効率を向上することが重要である。非特許文献１や非特許文献２、非特許文献３では、有機ＥＬ素子に共振器を導入し、干渉強め合い効果を利用することで、光取り出し効率を向上できることが示されている。さらに、非特許文献３では、共振器により外部量子効率が３５％向上したことが報告されている。 Therefore, in order to improve the light emission efficiency of the organic EL light emitting device, it is important to improve the light extraction efficiency. Non-Patent Document 1, Non-Patent Document 2, and Non-Patent Document 3 show that the light extraction efficiency can be improved by introducing a resonator into the organic EL element and utilizing the interference strengthening effect. Further, Non-Patent Document 3 reports that the external quantum efficiency is improved by 35% by the resonator.
これらとは別の従来技術として、特許文献１では、全反射を防ぎ素子内部への光閉じ込めを抑制することを目的として、有機層の上部や下部（光取り出し側やその反対側）に周期構造（回折格子）を配置する方法が提案されている。
しかしながら、共振器を設ける構成あるいは回折格子を設ける構成であっても、光取り出し効率の向上は不十分であり、さらなる光取り出し効率の向上が求められている。ところが、干渉光を生じさせるために平坦性が必要な共振器と、これとは逆に、回折光を生じさせるために凹凸性が必要な周期構造を両立させ、光取り出し効率をより向上するための深い研究が従来なされていなかった。 However, even with a configuration in which a resonator is provided or a configuration in which a diffraction grating is provided, improvement in light extraction efficiency is insufficient, and further improvement in light extraction efficiency is required. However, in order to improve the light extraction efficiency by combining a resonator that requires flatness to generate interference light and a periodic structure that requires unevenness to generate diffracted light, on the contrary. No deep research has been done in the past.
本発明は、上記課題に鑑み、従来の発光装置に比べて発光装置の光取り出し効率をさらに向上することを目的とする。 In view of the above-described problems, an object of the present invention is to further improve the light extraction efficiency of a light emitting device as compared with a conventional light emitting device.
上記背景技術の課題を解決するための手段として、本発明に係る発光装置は、基板と、前記基板の上に形成されている複数の発光素子とを有し、前記発光素子は、前記基板の上に形成されている反射電極である第１電極と、前記第１電極の上に形成されている発光層と、前記発光層の上に形成されている第２電極と、を有し、前記発光層で発光する光を、前記第１電極にある第１反射面と、前記第２電極にある第２反射面との間で共振させる共振器を有する発光装置において、前記発光層で発生し前記第１反射面と前記第２反射面との間を前記発光素子の面内方向に導波する光を前記発光素子の外に取り出す周期構造が、前記第１反射面に形成されており、前記周期構造は、前記発光素子の発光領域内に部分的に形成されており、前記基板垂直方向に沿った前記周期構造の高さｈが、外部に取り出される光のスペクトルのピーク波長λ、前記第１反射面と前記第２反射面との間の平均屈折率ｎに対して、ｈ＜λ／（４ｎ）を満たしていることを特徴とする。 As a means for solving the above problems of the background art, the light emitting device according to the present invention includes a base plate and a plurality of light emitting elements formed on the substrate, prior SL-emitting element, the A first electrode that is a reflective electrode formed on the substrate; a light emitting layer formed on the first electrode; and a second electrode formed on the light emitting layer. the light emitted from the light emitting layer, and a front Symbol first reflecting surface in the first electrodes, the light-emitting device having a resonator which resonates with the previous SL second reflecting surface in the second electrodes, A periodic structure for taking out the light generated in the light emitting layer and guided between the first reflecting surface and the second reflecting surface in the in-plane direction of the light emitting element to the outside of the light emitting element is the first reflecting surface. are formed on, the periodic structure is partially formed in the light emitting region of the light emitting element, the substrate vertical The height h of the periodic structure along the direction is such that the peak wavelength λ of the spectrum of the light extracted outside, and the average refractive index n between the first reflecting surface and the second reflecting surface, h < λ / (4n) is satisfied .
本発明によれば、従来の発光装置に比べて発光装置の光取り出し効率をさらに向上することが可能となる。 According to the present invention, it is possible to further improve the light extraction efficiency of the light emitting device as compared with the conventional light emitting device.
以下、本発明の原理を構成例に基づいて説明する。 Hereinafter, the principle of the present invention will be described based on structural examples.
本発明では、有機ＥＬ素子の光取り出し効率を向上させるために、共振器の内部に周期構造が構成される。周期構造は、発光層で発生し共振器を構成する２つの反射面の間を発光素子の面内方向に導波する光を発光素子の外に取り出す構造のことである。 In the present invention, a periodic structure is formed inside the resonator in order to improve the light extraction efficiency of the organic EL element. The periodic structure is a structure in which light that is generated in the light emitting layer and is guided between the two reflecting surfaces constituting the resonator in the in-plane direction of the light emitting element is extracted from the light emitting element.
共振器中に周期構造が構成された有機ＥＬ発光装置を模式的に表した断面概略図を図１に、平面概略図を図２に示す。なお、図示例では有機ＥＬ発光装置を示したが、無機ＥＬ発光装置やＱＤ−ＬＥＤ発光装置などであっても実施できる。図１において、１００は基板、１０１は有機層、１０２は反射電極、１０３Ｂは透明電極、１０４は金属半透明電極、１１０は素子分離層、３００は周期構造である。また、２０１は発光点、２０２は伝播光、２０３は導波光、２０４は回折光である。図２において、３０２はＥＬ発光領域である。 FIG. 1 is a schematic cross-sectional view schematically showing an organic EL light emitting device having a periodic structure in the resonator, and FIG. 2 is a schematic plan view thereof. In the illustrated example, an organic EL light-emitting device is shown, but an inorganic EL light-emitting device or a QD-LED light-emitting device can also be implemented. In FIG. 1, 100 is a substrate, 101 is an organic layer, 102 is a reflective electrode, 103B is a transparent electrode, 104 is a metal translucent electrode, 110 is an element isolation layer, and 300 is a periodic structure. Reference numeral 201 denotes a light emitting point, 202 denotes propagating light, 203 denotes guided light, and 204 denotes diffracted light. In FIG. 2, reference numeral 302 denotes an EL light emitting region.
図１に示した有機ＥＬ発光装置を構成する有機ＥＬ素子（発光素子）は、基板１００上に陽極として金属からなる反射電極１０２が形成されている。反射電極１０２には、基板１００と反対側の面の一部に金属により構成される周期構造３００が形成されており、周期構造の表面は、反射電極上の透明電極１０３Ｂにより覆われて平坦化されている。また、周期構造の表面を平坦化する平坦化層として、透明電極１０３Ｂのではなく、別に設けられる層であってもよい。なお、本実施の形態では反射電極１０２と透明電極１０３Ｂとが、基板１００側に設けられた第１電極である。 In the organic EL element (light emitting element) constituting the organic EL light emitting device shown in FIG. 1, a reflective electrode 102 made of metal is formed on a substrate 100 as an anode. In the reflective electrode 102, a periodic structure 300 made of metal is formed on a part of the surface opposite to the substrate 100, and the surface of the periodic structure is covered with a transparent electrode 103B on the reflective electrode and planarized. Has been. In addition, as a planarization layer for planarizing the surface of the periodic structure, a layer provided separately from the transparent electrode 103B may be used. In the present embodiment, the reflective electrode 102 and the transparent electrode 103B are the first electrodes provided on the substrate 100 side.
さらに、この陽極の周縁を覆うように絶縁材料からなる素子分離層１１０が形成されている。素子分離層１１０の開口部から露出する陽極の露出部の上に、発光層を含む有機層１０１が積層され、陰極である金属半透明電極１０４が形成されている。本実施の形態では金属半透明電極１０４を第２電極とする。 Further, an element isolation layer 110 made of an insulating material is formed so as to cover the periphery of the anode. On the exposed portion of the anode exposed from the opening of the element isolation layer 110, an organic layer 101 including a light emitting layer is laminated, and a metal translucent electrode 104 as a cathode is formed. In the present embodiment, the metal translucent electrode 104 is a second electrode.
周期構造は、凹部、凸部あるいは両方が面内に周期的に形成された構造のことである。周期構造の凹部、凸部は、図１に示すように直角の頂点を有するテーパ構造である必要はなく、順テーパ構造、逆テーパ構造等様々な構造にすることができる。周期構造３００は、金属により構成されており、図２に示すようにＥＬ発光領域３０２の内側にフォトニック結晶構造（周期構造３００）部分と平坦部分とをいずれも有している。なお、図１の反射電極１０２、透明電極１０３Ｂ、有機層１０１、金属半透明電極１０４が積層された部分に対応するのが、図２の発光領域（ＥＬ発光領域）３０２である。 The periodic structure is a structure in which concave portions, convex portions, or both are periodically formed in a plane. The concave and convex portions of the periodic structure do not need to be a tapered structure having a right apex, as shown in FIG. 1, and can have various structures such as a forward tapered structure and a reverse tapered structure. The periodic structure 300 is made of metal, and has a photonic crystal structure (periodic structure 300) portion and a flat portion inside the EL light emitting region 302 as shown in FIG. Note that a light emitting region (EL light emitting region) 302 in FIG. 2 corresponds to a portion where the reflective electrode 102, the transparent electrode 103B, the organic layer 101, and the metal translucent electrode 104 in FIG. 1 are stacked.
有機層１０１は、図３に示すように、通常、ホール輸送層１０６、発光層１０５（Ｒ発光層１１５、Ｇ発光層１２５、Ｂ発光層１３５）、電子輸送層１０７が積層された構成である。発光層１０５は、それぞれの発光色に応じた蛍光性有機化合物若しくは燐光性有機化合物を含む。また、必要に応じて陽極とホール輸送層１０６との間にホール注入層１０８を、陰極と電子輸送層１０７との間に電子注入層１０９を設けてもよい。 As shown in FIG. 3, the organic layer 101 usually has a structure in which a hole transport layer 106, a light emitting layer 105 (R light emitting layer 115, G light emitting layer 125, B light emitting layer 135), and an electron transport layer 107 are laminated. . The light emitting layer 105 includes a fluorescent organic compound or a phosphorescent organic compound corresponding to each emission color. Further, if necessary, a hole injection layer 108 may be provided between the anode and the hole transport layer 106, and an electron injection layer 109 may be provided between the cathode and the electron transport layer 107.
これらの有機ＥＬ素子に電圧を印加することで、陽極から注入された正孔と陰極から注入された電子が、有機層１０１中の発光層で再結合し、励起子を形成することで発光する。 By applying a voltage to these organic EL elements, holes injected from the anode and electrons injected from the cathode recombine in the light emitting layer in the organic layer 101 to emit light by forming excitons. .
図１に示した構成例では、反射電極１０２とその上の層（透明電極１０３Ｂ）の界面が第１反射面に、金属半透明電極１０４とその下の層（有機層）の界面が第２反射面となり、基板の法線方向（垂直方向）に１次元的な共振器が構成されている。つまり第１反射面は、発光層１０５よりも第１電極（反射電極１０２及び透明電極１０３Ｂ）側に設けられている反射面である。また第２反射面は発光層１０５よりも第２電極（金属半透明電極１０４）側に設けられている反射面である。 In the configuration example shown in FIG. 1, the interface between the reflective electrode 102 and the upper layer (transparent electrode 103B) is the first reflective surface, and the interface between the metal translucent electrode 104 and the lower layer (organic layer) is the second. A one-dimensional resonator is formed in the normal direction (vertical direction) of the substrate as a reflection surface. That is, the first reflecting surface is a reflecting surface provided on the first electrode (the reflecting electrode 102 and the transparent electrode 103B) side with respect to the light emitting layer 105. The second reflecting surface is a reflecting surface provided on the second electrode (metal translucent electrode 104) side with respect to the light emitting layer 105.
さらに、共振器の第１反射面と第２反射面との間の光路長（光学距離）は、有機ＥＬ素子の外部に取り出したい発光波長を干渉によって強め合うように構成されている。ここで、発光点２０１に対して、金属半透明電極１０４側（第２電極側）が光取り出し側、反射電極１０２側（第１電極側）が反射面側となる。 Furthermore, the optical path length (optical distance) between the first reflecting surface and the second reflecting surface of the resonator is configured to reinforce the emission wavelength desired to be extracted outside the organic EL element by interference. Here, with respect to the light emitting point 201, the metal translucent electrode 104 side (second electrode side) is the light extraction side, and the reflective electrode 102 side (first electrode side) is the reflective surface side.
一方、共振器は、同時に、基板面内方向（水平方向）では、プレーナー型の光導波路３０１として機能する。そのため、図４に示すような周期構造がない一般の有機ＥＬ素子の場合は、発光点２０１から発せられた光の大部分が、光導波路３０１を伝わる導波光２０３として有機ＥＬ素子の内部に閉じ込められる。つまり、導波光２０３は、第１反射面と第２反射面との間を有機ＥＬ素子の面内方向に導波する光のことである。これに対し、図１に示すような周期構造３００が配置された場合は、導波光２０３の一部が周期構造３００によって回折光２０４に変換されて有機ＥＬ素子の外に取り出され、光取り出し効率がさらに向上する。 On the other hand, the resonator simultaneously functions as a planar optical waveguide 301 in the in-plane direction (horizontal direction) of the substrate. Therefore, in the case of a general organic EL element having no periodic structure as shown in FIG. 4, most of the light emitted from the light emitting point 201 is confined inside the organic EL element as guided light 203 transmitted through the optical waveguide 301. It is done. That is, the guided light 203 is light that is guided between the first reflecting surface and the second reflecting surface in the in-plane direction of the organic EL element. On the other hand, when the periodic structure 300 as shown in FIG. 1 is arranged, a part of the guided light 203 is converted into the diffracted light 204 by the periodic structure 300 and extracted out of the organic EL element, and the light extraction efficiency is increased. Is further improved.
しかしながら、後述するように、共振器と周期構造を形式的に組み合わせても、双方を同時に機能させることはできず、光取り出し効率が向上するとは限らない。なぜなら、共振器は平坦な２つの反射面により光の干渉強め合いが生じるように構成されるが、共振器中に凹凸を有する周期構造を配置することで光の干渉強め合いが損なわれ、その結果、光取り出し効率の低下を招いてしまうためである。 However, as will be described later, even if the resonator and the periodic structure are combined formally, both cannot function simultaneously, and the light extraction efficiency is not always improved. This is because the resonator is configured so that light interference strengthening is generated by two flat reflecting surfaces, but by arranging a periodic structure having irregularities in the resonator, the light interference strengthening is impaired. As a result, the light extraction efficiency is reduced.
よって、光取り出し効率を向上するためには、共振器と周期構造を両立し、同時に機能させる必要がある。そこで、第１の方法として、共振器の干渉強め合い条件を保持するために周期構造の基板法線方向の高さを低く抑えることによって両立を図る。周期構造の高さを低くすることによって、周期構造が形成されている部分においても共振器による干渉強め合いの効果を得ることができる。 Therefore, in order to improve the light extraction efficiency, it is necessary to make the resonator and the periodic structure compatible and function simultaneously. Therefore, as a first method, in order to maintain the condition for strengthening the interference of the resonator, both are achieved by keeping the height of the periodic structure in the substrate normal direction low. By reducing the height of the periodic structure, the effect of strengthening interference by the resonator can be obtained even in the portion where the periodic structure is formed.
また、第２の方法として、発光素子の発光領域内に周期構造を形成する部分と、形成しない部分とを設ける。つまり、周期構造を発光領域内に部分的に設けることによって両立を図る。周期構造が設けられていない平坦な部分では、共振器による干渉強め合いの効果によって光取り出し効率の向上を図る。一方、周期構造が形成された部分では導波光を回折光に変換することによって光取り出し効率の向上を図る。さらには、周期構造が形成された部分でも共振器による干渉強め合いの効果を利用することもできる。 As a second method, a portion where the periodic structure is formed and a portion where the periodic structure is not formed are provided in the light emitting region of the light emitting element. In other words, both are achieved by providing the periodic structure partially in the light emitting region. In the flat portion where the periodic structure is not provided, the light extraction efficiency is improved by the effect of reinforcing the interference by the resonator. On the other hand, in the portion where the periodic structure is formed, the light extraction efficiency is improved by converting the guided light into diffracted light. Furthermore, the effect of strengthening interference by the resonator can also be used in the portion where the periodic structure is formed.
したがって、本発明により、有機ＥＬ素子において、共振器の干渉強め合い効果と周期構造の回折効果を同時に機能させ、光取り出し効率を向上することが可能となる。 Therefore, according to the present invention, in the organic EL element, the effect of strengthening the interference of the resonator and the diffraction effect of the periodic structure can be simultaneously functioned, and the light extraction efficiency can be improved.
以下、共振器の干渉強め合い効果と周期構造の回折効果を同時に機能させる方法についてより詳細な説明を行う。 In the following, a more detailed description will be given of a method for simultaneously functioning the resonance strengthening effect of the resonator and the diffraction effect of the periodic structure.
＜共振器＞
まず、共振器により干渉強め合い効果を得るための具体的条件について説明する。
<Resonator>
First, specific conditions for obtaining an interference strengthening effect by the resonator will be described.
共振器の第１反射面と第２反射面との間の光路長は、外部に取り出したい発光波長を干渉によって強め合うように設定されている。共振器の多重干渉による強め合い条件は、外部に取り出される光のスペクトルのピーク波長をλ、共振器を構成する第１反射面と第２反射面間の距離をｄ、第１反射面と第２反射面間の平均屈折率をｎとして数１で与えられる。ここで、第１反射面の位相シフト量と第２反射面の位相シフト量の和φ、整数ｍである。また、距離ｄと平均屈折率ｎは、共振器を構成する第１反射面と第２反射面との間の各層ｉの厚さをｄｉ、屈折率をｎｉとして、それぞれ、ｄ＝Σｄｉ、ｎ＝Σｎｉｄｉ／ｄで表される。 The optical path length between the first reflecting surface and the second reflecting surface of the resonator is set so as to intensify the emission wavelength desired to be extracted outside by interference. The strengthening condition due to the multiple interference of the resonator is that the peak wavelength of the spectrum of the light extracted outside is λ, the distance between the first reflecting surface and the second reflecting surface constituting the resonator is d, the first reflecting surface and the first reflecting surface The average refractive index between the two reflecting surfaces is given by Equation 1 where n is n. Here, the sum φ of the phase shift amount of the first reflecting surface and the phase shift amount of the second reflecting surface is an integer m. The distance d and the average refractive index n, the thickness d i of each layer i between the first reflection surface and the second reflecting surfaces constituting the resonator, the refractive index as n i, respectively, d = [Sigma] d i , n = Σn i d i / d.
ここで、第１反射面と第２反射面との間の光路長ｎｄは、外部に取り出される光のスペクトルのピーク波長λの０．３７５倍〜１．３７５倍程度であることが望ましい。また、有機ＥＬ素子では、第１反射面と第２反射面との間の平均屈折率はｎ＝１．５〜２．０程度であるから、第１反射面と第２反射面との間の距離ｄは、７０ｎｍより大きく７１５ｎｍより小さいことが望ましい。 Here, the optical path length nd between the first reflecting surface and the second reflecting surface is desirably about 0.375 to 1.375 times the peak wavelength λ of the spectrum of the light extracted outside. Further, in the organic EL element, since the average refractive index between the first reflecting surface and the second reflecting surface is about n = 1.5 to 2.0, it is between the first reflecting surface and the second reflecting surface. The distance d is preferably larger than 70 nm and smaller than 715 nm.
＜周期構造の高さ＞
次に、共振器と周期構造の両立を図るために、周期構造の高さを低く抑える構成について説明する。
<Height of periodic structure>
Next, a configuration for keeping the height of the periodic structure low in order to make the resonator and the periodic structure compatible will be described.
共振器に閉じ込められる導波光を有機ＥＬ素子の外に取り出すために、共振器の内部に周期構造を形成すると、周期構造の高さ方向の凹凸に従って場所ごとに光路長が変化し、共振器中の干渉波に影響を及ぼす。そのため、共振器の干渉強め合い条件を保持するために周期構造の基板法線方向の高さを低く抑えることが考えられる。 When a periodic structure is formed inside the resonator in order to extract guided light confined in the resonator from the organic EL element, the optical path length changes depending on the height of the periodic structure in accordance with the irregularities in the height direction, and the resonator Affects the interference wave. Therefore, it is conceivable to keep the height of the periodic structure in the normal direction of the substrate low in order to maintain the condition for strengthening the interference of the resonator.
このことを説明するために、共振器の第１反射面に周期構造が形成され、基板垂直方向に沿った周期構造の高さｈを変化させた場合の概念図を図５に示す。図５（ｃ）のように、周期構造の凹凸による光路長の変化が大きすぎると、干渉強め合いと干渉弱め合いが混在することになり、共振器の干渉強め合い効果が失われてしまう。 In order to explain this, FIG. 5 shows a conceptual diagram when a periodic structure is formed on the first reflecting surface of the resonator and the height h of the periodic structure along the substrate vertical direction is changed. As shown in FIG. 5C, when the change in the optical path length due to the irregularities of the periodic structure is too large, interference strengthening and interference weakening are mixed, and the interference strengthening effect of the resonator is lost.
したがって、共振器の干渉強め合いを保持するには、周期構造の凹凸いずれの領域においても、共振器の多重干渉による強め合い条件を満たす必要がある。つまり、周期構造の凹凸いずれの領域においても数１を満たす必要があり、数２の条件式で与えられる。さらに、数２から、周期構造の高さｈが満たすべき条件式が数３で与えられる。したがって、共振器の干渉強め合いを保持するためには、周期構造の高さｈを上限値λ／（４ｎ）より低く抑える必要がある。図５において、周期構造の高さが上限値λ／（４ｎ）より低い場合は、共振器の干渉強め合い効果が保たれる（図５（ｂ））。これに対し、周期構造の高さが上限値λ／（４ｎ）を越えると、共振器の干渉強め合い効果が失われる（図５（ｃ））。 Therefore, in order to maintain the interference strengthening of the resonator, it is necessary to satisfy the strengthening condition due to the multiple interference of the resonator in any of the irregularities of the periodic structure. That is, it is necessary to satisfy Equation 1 in any region of the irregularities of the periodic structure, which is given by the conditional expression of Equation 2. Furthermore, from Equation 2, the conditional expression to be satisfied by the height h of the periodic structure is given by Equation 3. Therefore, in order to maintain the interference strengthening of the resonator, it is necessary to keep the height h of the periodic structure lower than the upper limit value λ / (4n). In FIG. 5, when the height of the periodic structure is lower than the upper limit value λ / (4n), the interference strengthening effect of the resonator is maintained (FIG. 5B). On the other hand, when the height of the periodic structure exceeds the upper limit value λ / (4n), the interference strengthening effect of the resonator is lost (FIG. 5C).
有機ＥＬ素子では、平均屈折率は、ｎ＝１．５〜２．０程度、可視域での発光波長λは３８０ｎｍ〜７８０ｎｍであるから、周期構造の高さは、１３０ｎｍより小さいであることが望ましい。また、赤色発光素子、緑色発光素子、青色発光素子（以下Ｒ素子、Ｇ素子、Ｂ素子とする。）で周期構造の高さが共通の場合は、波長の最も短いＢ（青）で数３の条件を満たす必要があるため、６０ｎｍより小さいことが望ましい。Ｒ素子、Ｇ素子、Ｂ素子で周期構造の高さを共通にする場合、周期構造の形成をまとめて行うことができる。さらに、発光層の段切れを防いで電流リークや発光不均一化を防ぐためには発光層の平坦化が求められ、発光層の平坦化のためには、周期構造の高さが３０ｎｍより小さことがより望ましい。特に、有機ＥＬ素子においては、有機層（発光層）の段切れによる電流リークや発光不均一化の問題が顕著であるため、周期構造の高さを低くすることが好ましい。 In the organic EL element, the average refractive index is about n = 1.5 to 2.0, and the emission wavelength λ in the visible range is 380 nm to 780 nm. Therefore, the height of the periodic structure may be smaller than 130 nm. desirable. Further, when the red light emitting element, the green light emitting element, and the blue light emitting element (hereinafter referred to as “R element”, “G element”, and “B element”) have a common height of the periodic structure, B (blue) having the shortest wavelength is represented by several 3 Since it is necessary to satisfy the above condition, it is desirable that the thickness is smaller than 60 nm. When the height of the periodic structure is shared by the R element, the G element, and the B element, the periodic structure can be formed collectively. Furthermore, in order to prevent the light emitting layer from being disconnected and to prevent current leakage and light emission non-uniformity, the light emitting layer needs to be flattened. For the flattening of the light emitting layer, the height of the periodic structure is smaller than 30 nm. Is more desirable. In particular, in an organic EL element, problems such as current leakage and non-uniform light emission due to disconnection of the organic layer (light emitting layer) are significant, and therefore it is preferable to reduce the height of the periodic structure.
とはいえ周期構造は、発光層よりも基板側に形成する、つまり発光層と基板との間に形成することが好ましい。発光層の光取り出し側に形成する場合、周期構造による発光層の段切れの問題は解決されるが、発光層（有機層）に影響を与えることなく周期構造を形成することが困難であるためである。 However, the periodic structure is preferably formed on the substrate side of the light emitting layer, that is, between the light emitting layer and the substrate. When forming on the light extraction side of the light emitting layer, the problem of step breakage of the light emitting layer due to the periodic structure is solved, but it is difficult to form the periodic structure without affecting the light emitting layer (organic layer). It is.
一方、導波光から回折光への結合効率を大きくし、周期構造の回折効果を向上させるためには、周期構造による光導波路の誘電率変化を大きくすることが望ましい。数３から周期構造の高さを抑える必要があるため、周期構造の体積は限定される。したがって、誘電率変化を大きくするために、有機層や透明導電層（透明電極）などに対して誘電率が大きく異なる材料で周期構造を構成することが望ましい。このためには、金属層によって周期構造を形成することが望ましい。さらに、共振器を構成する反射界面に周期構造が構成されることが望ましい。反射面を構成する層を形成する際に周期構造も形成することができるため、周期構造を形成するために別の層を設ける必要がないからである。 On the other hand, in order to increase the coupling efficiency from guided light to diffracted light and improve the diffraction effect of the periodic structure, it is desirable to increase the change in the dielectric constant of the optical waveguide due to the periodic structure. Since it is necessary to suppress the height of the periodic structure from Equation 3, the volume of the periodic structure is limited. Therefore, in order to increase the change in the dielectric constant, it is desirable that the periodic structure is made of a material having a significantly different dielectric constant from that of the organic layer or the transparent conductive layer (transparent electrode). For this purpose, it is desirable to form a periodic structure with a metal layer. Furthermore, it is desirable that a periodic structure is formed on the reflective interface that forms the resonator. This is because a periodic structure can also be formed when forming the layer constituting the reflecting surface, and thus it is not necessary to provide another layer to form the periodic structure.
したがって、共振器を有する有機ＥＬ素子において、共振器の内部に金属層によって構成製される周期構造を構成することにより、共振器の干渉強め合い効果と周期構造の回折効果を同時に機能させることができ、光取り出し効率を向上することが可能となる。 Therefore, in an organic EL element having a resonator, by forming a periodic structure made of a metal layer inside the resonator, it is possible to simultaneously function the interference strengthening effect of the resonator and the diffraction effect of the periodic structure. It is possible to improve the light extraction efficiency.
ここで、具体的な評価例として、金属層によって構成される周期構造の高さと発光強度の関係を数値計算により評価した結果を図６にグラフとして示す。発光強度は、周期構造の高さが０の時を基準とした相対値であり、光取り出し効率の変化を示している。図５のように、第１反射面の全面に周期構造が配置されているとし、周期構造の高さｈの中心線から第２反射面までの距離ｄを一定として、周期構造の高さｈを変化させた。電磁波の数値計算には、有機ＥＬ発光装置の断面を考え、ＦＤＴＤ法を用いた。波長範囲λ＝３８０ｎｍ〜７８０ｎｍで、５ｎｍ刻みで計算を行った。電磁波モードは、ＴＥ、ＴＭモードで計算を行った。 Here, as a specific evaluation example, the result of evaluating the relationship between the height of the periodic structure constituted by the metal layer and the light emission intensity by numerical calculation is shown as a graph in FIG. The light emission intensity is a relative value based on when the height of the periodic structure is 0, and indicates a change in light extraction efficiency. As shown in FIG. 5, it is assumed that the periodic structure is arranged on the entire surface of the first reflecting surface, the distance d from the center line of the height h of the periodic structure to the second reflecting surface is constant, and the height h of the periodic structure is set. Changed. For the numerical calculation of electromagnetic waves, the FDTD method was used considering the cross section of the organic EL light emitting device. The calculation was performed in 5 nm increments in the wavelength range λ = 380 nm to 780 nm. The electromagnetic wave mode was calculated in the TE and TM modes.
図６の評価例では、外部に取り出される光のスペクトルのピーク波長λが約５３０ｎｍ、共振器を構成する第１反射面と第２反射面間の平均屈折率ｎが約１．９であるから、周期構造の高さｈの上限値λ／（４ｎ）は約７０ｎｍである。 In the evaluation example of FIG. 6, the peak wavelength λ of the spectrum of the light extracted outside is about 530 nm, and the average refractive index n between the first reflecting surface and the second reflecting surface constituting the resonator is about 1.9. The upper limit value λ / (4n) of the height h of the periodic structure is about 70 nm.
図６の評価結果のグラフにおいて、属層によって構成される周期構造の高さを徐々に高くしていくと、発光強度が増加していき、高さが４０ｎｍ付近で発光強度が最大となる。その後、減少に転じ、周期構造の高さが上限値７０ｎｍ付近で、曲線は変曲点をとる。さらに、周期構造の高さが上限値７０ｎｍより高くなると、発光強度は減少を続け、最終的に、周期構造がない場合の５０％程度にまで発光強度が減少してしまうことが理解できる。 In the graph of the evaluation results in FIG. 6, when the height of the periodic structure constituted by the genus layer is gradually increased, the emission intensity increases, and the emission intensity becomes maximum when the height is around 40 nm. Thereafter, the curve starts to decrease, and the curve takes an inflection point when the height of the periodic structure is around the upper limit of 70 nm. Furthermore, it can be understood that when the height of the periodic structure is higher than the upper limit of 70 nm, the emission intensity continues to decrease, and finally the emission intensity decreases to about 50% of the case where there is no periodic structure.
＜周期構造の部分的形成＞
次に、共振器と周期構造の両立を図るために、周期構造を発光領域内に部分的に設ける構成について説明する。周期構造を発光領域内に部分的に設けることによっても、共振器と周期構造を同時に機能させ光取り出し効率を向上させることができる。
<Partial formation of periodic structure>
Next, a configuration in which the periodic structure is partially provided in the light emitting region in order to achieve compatibility between the resonator and the periodic structure will be described. Also by providing the periodic structure partially in the light emitting region, the resonator and the periodic structure can function simultaneously to improve the light extraction efficiency.
図２に示すように、本構成例では、周期構造３００が存在する部分と存在しない部分から構成される。ここで、周期構造３００の周期を規定する２つの基本格子ベクトルをａ１、ａ２とする。また、これらの基本格子ベクトルａ１、ａ２に対し、数４の関係を満たす基本逆格子ベクトルをｂ１、ｂ２とする。 As shown in FIG. 2, this configuration example includes a portion where the periodic structure 300 exists and a portion where the periodic structure 300 does not exist. Here, it is assumed that two basic lattice vectors defining the period of the periodic structure 300 are a 1 and a 2 . In addition, for these basic lattice vectors a 1 and a 2 , basic reciprocal lattice vectors satisfying the relationship of Equation 4 are b 1 and b 2 .
周期構造を発光領域内に部分的に設ける場合、共振器中に周期構造を形成する部分と周期構造を形成せずに共振器の平坦性を維持する部分とが交互に構成されることが望ましい。図２の例では、周期構造３００が存在する部分と存在しない部分が、より大きな周期で配列された階層構造となっている。ここで、より大きな周期を規定する２つの基本格子ベクトルはＡ１、Ａ２である。図２の例では、発光素子の上下左右で同じ視野角特性となるように、周期構造３００が４回対称性を有する構造となっている。本発明の発光素子を表示装置として用いる場合には、表示装置の上下左右の視野角特性を同じにするために、周期構造の基本格子ベクトル方向と表示領域の上下方向、左右方向を合わせることが好ましい。 When the periodic structure is partially provided in the light emitting region, it is desirable that the portion that forms the periodic structure in the resonator and the portion that maintains the flatness of the resonator without forming the periodic structure are alternately configured. . In the example of FIG. 2, there is a hierarchical structure in which a portion where the periodic structure 300 exists and a portion where the periodic structure 300 does not exist are arranged with a larger period. Here, two basic lattice vectors that define a larger period are A 1 and A 2 . In the example of FIG. 2, the periodic structure 300 has a four-fold symmetry so that the same viewing angle characteristics are obtained at the top, bottom, left, and right of the light emitting element. When the light emitting element of the present invention is used as a display device, the basic lattice vector direction of the periodic structure and the vertical and horizontal directions of the display region can be matched with each other in order to make the vertical and horizontal viewing angle characteristics of the display device the same. preferable.
図１において、導波光２０３が減衰により強度が半減する距離（半減距離）は１０μｍ程度である。よって、周期構造３００が存在しない部分で発光した光が、周期構造３００まで到達して素子外部に取り出され、光取り出し効率が向上するためには、発光領域内のいずれの位置からも、最も近い周期構造までの距離が１０μｍより小さいことが望ましい。 In FIG. 1, the distance that the intensity of the guided light 203 is reduced by half due to attenuation (half distance) is about 10 μm. Therefore, light emitted from a portion where the periodic structure 300 does not exist reaches the periodic structure 300 and is extracted to the outside of the device. In order to improve light extraction efficiency, it is closest from any position in the light emitting region. It is desirable that the distance to the periodic structure is smaller than 10 μm.
ここで、本構成例（図１、図２：周期構造あり、共振器あり）と従来例（図４：周期構造なし、共振器あり）の発光スペクトルを、数値計算により評価した例を図７にグラフで示す。本構成例のピーク強度が、従来例のピーク強度に対して、約１．８倍となり、光取り出し効率が向上することがわかる。 Here, an example in which the emission spectra of the present configuration example (FIG. 1, FIG. 2: with periodic structure and with resonator) and the conventional example (FIG. 4: without periodic structure and with resonator) are evaluated by numerical calculation are shown in FIG. Is shown in a graph. It can be seen that the peak intensity of this configuration example is about 1.8 times the peak intensity of the conventional example, and the light extraction efficiency is improved.
＜周期構造の周期＞
周期構造による回折の効果を高めるためには、周期構造の周期を設定することがより好ましい。以下周期構造の周期について説明する。
<Period of periodic structure>
In order to enhance the effect of diffraction by the periodic structure, it is more preferable to set the period of the periodic structure. Hereinafter, the period of the periodic structure will be described.
有機層１０１中の発光層からの発光ピーク波長をλとし、波数をｋ＝２π／λとする。また、発光層の屈折率をｎ、光取り出し側媒体（通常は空気）の屈折率をｎｅｘｔとし、条件ｎ＞ｎｅｘｔを満たすとする。 The emission peak wavelength from the light emitting layer in the organic layer 101 is λ, and the wave number is k = 2π / λ. Further, it is assumed that the refractive index of the light emitting layer is n, the refractive index of the light extraction side medium (usually air) is n ext , and the condition n> n ext is satisfied.
光導波路３０１を伝播する導波光２０３に対する基板１００の水平方向への伝播係数をβとし、導波光２０３に対する有効屈折率ｎｅｆｆ及び有効吸収係数κｅｆｆを、数５により定義する。有効屈折率ｎｅｆｆは、条件ｎｅｘｔ＜ｎｅｆｆ＜ｎを満たす。 The propagation coefficient in the horizontal direction of the substrate 100 with respect to the guided light 203 propagating through the optical waveguide 301 is β, and the effective refractive index n eff and the effective absorption coefficient κ eff for the guided light 203 are defined by Equation 5. The effective refractive index n eff satisfies the condition n ext <n eff <n.
このとき、回折条件は水平方向の位相整合条件から、２つの整数ｍ１、ｍ２を回折次数とし、基板法線方向に対する回折角度をθとして、条件ｎｅｘｔ＜ｎｅｆｆ＜ｎのもとで、数６で与えられる。 At this time, the diffraction condition is based on the condition of n ext <n eff <n, where two integers m 1 and m 2 are diffraction orders and the diffraction angle with respect to the substrate normal direction is θ, based on the phase matching condition in the horizontal direction. , Given by equation (6).
正方格子の場合は、周期をａとして、基本格子ベクトルは数７となり、基本逆格子ベクトルは数８となる。 In the case of a square lattice, the period is a, the basic lattice vector is Equation 7, and the basic reciprocal lattice vector is Equation 8.
この時、数６の回折条件は、数９となる。 At this time, the diffraction condition of Formula 6 is expressed by Formula 9.
ここで、どちらか一方の１次元方向に着目し、ｍ２＝０（もしくは、ｍ１＝０）および、｜ｍ１｜＝ｍ＞０（もしくは、｜ｍ２｜＝ｍ＞０）とする。この時、数９の回折条件は、簡略化され数１０となる。さらに、有機ＥＬ素子のように、３ｎｅｘｔ＞ｎ≧ｎｅｆｆの関係を満たす場合、ｍ＝１の１次の回折光のみが生じるための回折条件は、数１１となる。 Here, paying attention to one of the one-dimensional directions, m 2 = 0 (or m 1 = 0) and | m 1 | = m> 0 (or | m 2 | = m> 0). . At this time, the diffraction condition of Equation 9 is simplified to become Equation 10. Further, when the relationship of 3n ext > n ≧ n eff is satisfied as in the case of an organic EL element, the diffraction condition for generating only the first-order diffracted light with m = 1 is expressed by Equation 11.
有機ＥＬ素子の発光パターンや効率、色度などの制御を可能とするには、１次の回折光のみを発生させ、また、導波光のモード数を少なくすることが望ましい。有機ＥＬ素子では、通常、発光層の屈折率はｎ＝１．６〜２．０程度、光取り出し側の屈折率はｎｅｘｔ＝１．０である。よって、数１１から、主に１次の回折光のみを利用する場合は、周期構造３００の周期ａは、概ね発光ピーク波長λの０．３３倍〜１．０倍が望ましい。可視光の波長域が３８０ｎｍ〜７８０ｎｍであることから、周期構造３００の周期ａは、１２５ｎｍより大きく７８０ｎｍより小さいことが望ましい。Ｒ素子、Ｇ素子、Ｂ素子のそれぞれで周期構造の周期が数１１を満たすためには、Ｒ素子の周期を最も長く、Ｂ素子の周期を最も短くすることが好ましい。 In order to enable control of the light emission pattern, efficiency, chromaticity, and the like of the organic EL element, it is desirable to generate only the first-order diffracted light and reduce the number of modes of guided light. In the organic EL element, the refractive index of the light emitting layer is usually about n = 1.6 to 2.0, and the refractive index on the light extraction side is n ext = 1.0. Therefore, from Equation 11, when only the first-order diffracted light is mainly used, the period a of the periodic structure 300 is preferably approximately 0.33 to 1.0 times the emission peak wavelength λ. Since the wavelength range of visible light is 380 nm to 780 nm, the period a of the periodic structure 300 is desirably larger than 125 nm and smaller than 780 nm. In order for the period of the periodic structure to satisfy Equation 11 in each of the R element, the G element, and the B element, it is preferable that the period of the R element is the longest and the period of the B element is the shortest.
＜その他の構成＞
これまでは、基板側を陽極、光取り出し側を陰極とする構成で説明してきたが、基板側を陰極、光取り出し側を陽極とし、ホール輸送層、発光層、電子輸送層を逆順に積層した構成においても本発明を実施することは可能である。したがって、本発明にかかる発光装置は基板側を陽極、光取り出し側を陰極とする構成に限定されるものではない。
<Other configurations>
So far, the substrate side has been described as an anode and the light extraction side as a cathode. However, the substrate side is a cathode, the light extraction side is an anode, and a hole transport layer, a light emitting layer, and an electron transport layer are stacked in reverse order. It is possible to implement the present invention even in the configuration. Therefore, the light emitting device according to the present invention is not limited to the configuration in which the substrate side is an anode and the light extraction side is a cathode.
また、図３のホール輸送層１０６、発光層１０５、電子輸送層１０７、ホール注入層１０８、電子注入層１０９に用いられる有機化合物としては、低分子材料、高分子材料、若しくはその両方により構成され、特に限定されるものではない。さらに、必要に応じて無機化合物やＱＤ（量子ドット）を用いてもよい。 Further, the organic compound used for the hole transport layer 106, the light emitting layer 105, the electron transport layer 107, the hole injection layer 108, and the electron injection layer 109 in FIG. 3 is composed of a low molecular material, a polymer material, or both. There is no particular limitation. Furthermore, you may use an inorganic compound and QD (quantum dot) as needed.
さらに、周期構造３００は、上述したように２次元的なフォトニック結晶構造に限定されず、１次元的な回折格子の組み合わせや３次元的なフォトニック結晶構造でもよい。また、図１では凹型のフォトニック結晶構造を示したが、図８のように凸型のフォトニック結晶構造でもよい。また、図９のように、周期構造を反射界面から離した位置に構成しても良い。 Furthermore, the periodic structure 300 is not limited to the two-dimensional photonic crystal structure as described above, and may be a combination of a one-dimensional diffraction grating or a three-dimensional photonic crystal structure. 1 shows a concave photonic crystal structure, a convex photonic crystal structure may be used as shown in FIG. Further, as shown in FIG. 9, the periodic structure may be arranged at a position away from the reflective interface.
さらに、図１０のように、異なる基本格子ベクトルを持つ複数種類の周期構造３００をいずれも有する構成であってもよい。図１０の例は、基本格子ベクトルａ１、ａ２の周期構造と基本格子ベクトルａ’１、ａ’２の周期構造を組み合わせた場合である。ａ’１は（ａ１＋ａ２）／√２方向のベクトルであり、ａ’２は（−ａ１＋ａ２）／√２方向のベクトルである。つまり、周期構造は、４回対称性を有する周期構造１と、周期構造１を４５°回転した周期構造２を組み合わせた構造になっている。図１０のように周期構造を配置することにより、発光素子の上下方向と左右方向の視野角特性だけでなく、発光素子の斜め方向の視野角特性も同じにすることができる。また、同様に、周期構造は、Ｎを自然数として、Ｎ回対称性を有する周期構造１と、周期構造１を１８０°／Ｎ回転した周期構造２を組み合わせた構造とすることができる。 Furthermore, as shown in FIG. 10, the structure may include any of a plurality of types of periodic structures 300 having different basic lattice vectors. The example of FIG. 10 is a case where the periodic structure of the basic lattice vectors a 1 and a 2 and the periodic structure of the basic lattice vectors a ′ 1 and a ′ 2 are combined. a ′ 1 is a vector in the (a 1 + a 2 ) / √2 direction, and a ′ 2 is a vector in the (−a 1 + a 2 ) / √2 direction. That is, the periodic structure is a structure in which the periodic structure 1 having four-fold symmetry and the periodic structure 2 obtained by rotating the periodic structure 1 by 45 ° are combined. By arranging the periodic structure as shown in FIG. 10, not only the vertical and horizontal viewing angle characteristics of the light emitting element but also the oblique viewing angle characteristics of the light emitting element can be made the same. Similarly, the periodic structure can be a structure in which N is a natural number and the periodic structure 1 having N-fold symmetry and the periodic structure 2 obtained by rotating the periodic structure 1 by 180 ° / N are combined.
周期構造３００は、完全に周期的である必要はなく、準結晶構造やフラクタル構造、連続的に周期構造が変化する構造、部分的に不規則な散乱構造を有する構造、若しくは周期構造とこれらを組み合わせたものでもよい。 The periodic structure 300 does not need to be completely periodic, but includes a quasicrystalline structure, a fractal structure, a structure in which the periodic structure continuously changes, a structure having a partially irregular scattering structure, or a periodic structure. It may be a combination.
さらに、以上の説明では、基板側の電極、即ち第１電極が反射電極と透明電極の２層の電極である構成で説明してきたが、いずれか１層の電極とする構成においても本発明を実施可能である。第１電極を透明電極とする場合、基板側に接して、あるいは離間して金属層によって構成される反射層を設けることが好ましい。この反射層が、第１反射面となる。 Further, in the above description, the electrode on the substrate side, that is, the first electrode has been described as a two-layer electrode of a reflective electrode and a transparent electrode, but the present invention is also applied to a configuration in which any one of the electrodes is used. It can be implemented. When the first electrode is a transparent electrode, it is preferable to provide a reflective layer composed of a metal layer in contact with or apart from the substrate side. This reflective layer becomes the first reflective surface.
さらに、以上の説明では、光取り出し側の電極、即ち第２電極が金属半透明電極である構成で説明してきたが、図１１に示すように、光取り出し側の電極を透明電極（光透過電極）１０３とする構成においても本発明を実施可能である。この場合、第２反射面は、透明電極１０３と隣接する気体（空気）との界面になる。また、図１の半透明電極１０４の上や図１１の透明電極１０３の上には、図１２に示すように誘電体層１０４Ｂが形成されていてもよい。あるいは、第１反射面と第２反射面のうち光取り出し側に位置する反射面を、金属、透明電極、誘電体層のいずれかもしくは全部の組み合わせによる多層干渉膜とすることも可能である。 Further, in the above description, the light extraction side electrode, that is, the second electrode is a metal translucent electrode. However, as shown in FIG. 11, the light extraction side electrode is a transparent electrode (light transmission electrode). ) 103 can be implemented even in the configuration of 103. In this case, the second reflecting surface is an interface between the transparent electrode 103 and the adjacent gas (air). Further, a dielectric layer 104B may be formed on the translucent electrode 104 in FIG. 1 or on the transparent electrode 103 in FIG. 11 as shown in FIG. Alternatively, the reflective surface located on the light extraction side of the first reflective surface and the second reflective surface can be a multilayer interference film made of any one or all of metals, transparent electrodes, and dielectric layers.
さらに、以上の説明では、基板の反対側が光取り出し側となるトップエミッション型の構成について説明してきたが、基板側が光取り出し側となるボトムエミッション構成においても本発明は実施可能である。図１３では、発光層より基板側に位置する反射面に周期構造を形成する例としている。すなわち、基板１００上に周期構造３００を有する金属半透明電極１０４と反射電極上の透明電極１０３Ｂを形成し、その上に有機層１０１、反射電極１０２を積層したボトムエミッション構成を示している。 Furthermore, in the above description, the top emission type configuration in which the opposite side of the substrate is the light extraction side has been described, but the present invention can also be implemented in a bottom emission configuration in which the substrate side is the light extraction side. FIG. 13 shows an example in which a periodic structure is formed on the reflecting surface located on the substrate side of the light emitting layer. That is, a bottom emission configuration is shown in which a metal translucent electrode 104 having a periodic structure 300 and a transparent electrode 103B on a reflective electrode are formed on a substrate 100, and an organic layer 101 and a reflective electrode 102 are laminated thereon.
さらに、図２において、金属からなる反射電極１０２と可視光の波長領域では誘電体とみなせる反射電極上の透明電極１０３Ｂとの界面（金属反射面）を基板水平方向に伝播し、導波光の一種と考えられる表面プラズモンが生じる。よって、反射電極１０２と反射電極上の透明電極１０３Ｂとの界面を光導波路として利用可能である。表面プラズモンの伝播係数βｓｐを、数５の伝播係数βとすると、通常の導波光と同様に回折条件は数６で与えられる。表面プラズモンを生じる界面は、金属層と透明導電層の界面に限られず、金属層と有機層界面や金属と誘電体層界面でもよい。 Further, in FIG. 2, an interface (metal reflective surface) between the reflective electrode 102 made of metal and the transparent electrode 103B on the reflective electrode that can be regarded as a dielectric in the visible wavelength region propagates in the horizontal direction of the substrate, and is a kind of guided light. Surface plasmon that is considered to occur. Therefore, the interface between the reflective electrode 102 and the transparent electrode 103B on the reflective electrode can be used as an optical waveguide. If the propagation coefficient β sp of the surface plasmon is the propagation coefficient β of Equation 5, the diffraction condition is given by Equation 6, as in the case of ordinary guided light. The interface for generating the surface plasmon is not limited to the interface between the metal layer and the transparent conductive layer, but may be the interface between the metal layer and the organic layer or the interface between the metal and the dielectric layer.
本発明の発光装置は、表示装置や、照明、表示装置用のバックライト等の様々な用途に適用することができる。表示装置としては、テレビ受像機、パーソナルコンピュータのディスプレイ、撮像装置の背面表示部、携帯電話の表示部、携帯音楽再生装置の表示部、携帯情報端末（ＰＤＡ）の表示部、携帯ゲーム機の表示部、カーナビゲーションシステムの表示部等がある。 The light emitting device of the present invention can be applied to various uses such as a display device, illumination, and a backlight for the display device. As a display device, a television receiver, a display of a personal computer, a rear display unit of an imaging device, a display unit of a mobile phone, a display unit of a portable music player, a display unit of a personal digital assistant (PDA), a display of a portable game machine And a display unit of a car navigation system.
以下、本発明の発光装置の製造方法を実施例として説明するが、本発明は本実施例によって何ら限定されるものではない。 Hereinafter, although the manufacturing method of the light-emitting device of this invention is demonstrated as an Example, this invention is not limited at all by this Example.
＜実施例１＞
図１４に示す構成のフルカラー有機ＥＬ発光装置を以下に示す方法で作製する。つまり、本実施例１の発光装置は、複数の画素を有し、各画素がＲ素子、Ｇ素子、Ｂ素子、つまり赤、緑、青の３色の副画素からなる有機ＥＬ発光装置であって、表示装置として好ましく適用することができる例である。
<Example 1>
A full-color organic EL light-emitting device having the configuration shown in FIG. 14 is manufactured by the following method. That is, the light-emitting device of Example 1 is an organic EL light-emitting device having a plurality of pixels, and each pixel is composed of R elements, G elements, and B elements, that is, red, green, and blue subpixels. This is an example that can be preferably applied as a display device.
まず、支持体としてのガラス基板上に、低温ポリシリコンからなるＴＦＴ駆動回路を形成し、その上にアクリル樹脂からなる平坦化層を形成して基板１００とする。基板１００上に、反射電極１０２として、スパッタリングによりＡｇ合金を約１５０ｎｍの膜厚で形成する。Ａｇ合金からなる反射電極１０２は、可視光の波長域（λ＝３８０ｎｍ〜７８０ｎｍ）で分光反射率８０％以上の高反射電極である。Ａｇ合金以外に、Ａｌ合金などを用いてもよい。 First, a TFT driving circuit made of low-temperature polysilicon is formed on a glass substrate as a support, and a planarizing layer made of acrylic resin is formed on the TFT driving circuit. On the substrate 100, as the reflective electrode 102, an Ag alloy is formed to a thickness of about 150 nm by sputtering. The reflective electrode 102 made of an Ag alloy is a highly reflective electrode having a spectral reflectance of 80% or more in the visible light wavelength range (λ = 380 nm to 780 nm). In addition to the Ag alloy, an Al alloy or the like may be used.
この反射電極１０２上に、まず、ポジ型のレジストをスピンコートしプリベークを行う。その後、レジストに図２に示すような正方格子の周期構造パターンを露光し、現像、ポストベークを行いレジストパターンを形成する。 First, a positive resist is spin-coated on the reflective electrode 102 and prebaked. Thereafter, a periodic structure pattern of a square lattice as shown in FIG. 2 is exposed to the resist, and development and post-baking are performed to form a resist pattern.
エッチング加工により、反射電極１０２表面に周期構造３００を形成する。本実施例１では、Ｒ素子の周期構造（Ｒ周期構造３１０）は周期３４５ｎｍ、一辺の長さ２００ｎｍ、エッチング深さ４０ｎｍとされる。Ｇ素子の周期構造（Ｇ周期構造３２０）は周期２５０ｎｍ、一辺の長さ１４０ｎｍ、エッチング深さ４０ｎｍとされる。Ｂ素子の周期構造（Ｂ周期構造３３０）は周期２００ｎｍ、一辺の長さ１４５ｎｍ、エッチング深さ４０ｎｍとされる。また、ＲＧＢの各素子で、１０周期ごとに周期構造３００が存在する部分と平坦な部分とが交互に並んでいる。 The periodic structure 300 is formed on the surface of the reflective electrode 102 by etching. In Example 1, the periodic structure of the R element (R periodic structure 310) has a period of 345 nm, a side length of 200 nm, and an etching depth of 40 nm. The periodic structure of the G element (G periodic structure 320) has a period of 250 nm, a side length of 140 nm, and an etching depth of 40 nm. The periodic structure of the B element (B periodic structure 330) has a period of 200 nm, a side length of 145 nm, and an etching depth of 40 nm. In each of the RGB elements, the portion where the periodic structure 300 exists and the flat portion are alternately arranged every 10 cycles.
次に、ＩＺＯのリフトオフ加工により、周期構造３００の凹状に窪んだエッチング部分を平坦化する。レジストパターンを残した状態で、スパッタリングにより透明導電性材料のＩＺＯを４０ｎｍの膜厚で形成する。エッチング部分ではＡｇ合金上にＩＺＯを、エッチング部分以外ではレジスト上にＩＺＯを形成する。その後、レジストを剥離し、レジスト上のＩＺＯごと取り除いて平坦化する。この上に、スパッタリングによりＩＺＯを２０ｎｍの膜厚で形成して電極のパターニングをし、フォトニック結晶付きの陽極を形成する。 Next, the etched portion of the periodic structure 300 that has been recessed is flattened by lift-off processing of IZO. With the resist pattern left, IZO, which is a transparent conductive material, is formed to a thickness of 40 nm by sputtering. In the etched portion, IZO is formed on the Ag alloy, and in other portions than the etched portion, IZO is formed on the resist. Thereafter, the resist is peeled off, and the entire IZO on the resist is removed and flattened. On top of this, IZO is formed to a thickness of 20 nm by sputtering to pattern the electrode, thereby forming an anode with a photonic crystal.
図２のような正方格子では、各副画素の上下方向と左右方向とで周期構造３１０（３２０、３３０）の周期（配列）が等しい。そのため、発光装置を視認した場合、上下方向と左右方向とで同様の光学特性を得ることができ、視認性を高めることができる。また、逆に、上下方向と左右方向の周期が異なる四角格子としてもよい。この場合は、方向によって視認性を調整することが可能となる。さらに、図１０のように、異なる正方格子を組み合わせることにより、上下方向、左右方向と斜め方向とで同様の光学特性を得ることができ、視認性を高めることができる。 In the square lattice as shown in FIG. 2, the period (array) of the periodic structures 310 (320, 330) is equal in the vertical direction and the horizontal direction of each subpixel. Therefore, when the light emitting device is visually recognized, similar optical characteristics can be obtained in the vertical direction and the horizontal direction, and visibility can be improved. Conversely, a quadrangular lattice having different vertical and horizontal periods may be used. In this case, the visibility can be adjusted depending on the direction. Furthermore, as shown in FIG. 10, by combining different square lattices, similar optical characteristics can be obtained in the vertical direction, the horizontal direction, and the diagonal direction, and visibility can be improved.
さらに、酸化窒化珪素（ＳｉＮｘＯｙ）の素子分離層１１０を３２０ｎｍの膜厚で形成した後、各副画素にＥＬ発光領域となる開口部をエッチングし、フォトニック結晶を配置した陽極基板を作製する。 Further, after forming an element isolation layer 110 of silicon oxynitride (SiN x O y ) with a thickness of 320 nm, an opening serving as an EL light emitting region is etched in each subpixel, and an anode substrate on which a photonic crystal is arranged is formed. Make it.
これをイソプロピルアルコール（ＩＰＡ）で超音波洗浄し、次いで、煮沸洗浄後乾燥する。その後、ＵＶ／オゾン洗浄してからＲ、Ｇ、Ｂそれぞれの有機層１１１、１２１、１３１を真空蒸着により形成する。 This is subjected to ultrasonic cleaning with isopropyl alcohol (IPA) and then dried after boiling and drying. Then, after UV / ozone cleaning, R, G, and B organic layers 111, 121, and 131 are formed by vacuum deposition.
まず、下記構造式で示される化合物［Ｉ］を、シャドーマスクを用いて各副画素に、Ｒホール輸送層として２１５ｎｍの膜厚、Ｇホール輸送層として１５５ｎｍの膜厚、Ｂホール輸送層として１０５ｎｍの膜厚で形成する。この際の真空度は１×１０−４Ｐａ、蒸着レートは、０．２ｎｍ／ｓｅｃである。 First, compound [I] represented by the following structural formula is applied to each subpixel using a shadow mask, with a film thickness of 215 nm as an R hole transport layer, a film thickness of 155 nm as a G hole transport layer, and 105 nm as a B hole transport layer. The film thickness is formed. The degree of vacuum at this time is 1 × 10 −4 Pa, and the deposition rate is 0.2 nm / sec.
次に、発光層として、シャドーマスクを用いて、Ｒ素子、Ｇ素子、Ｂ素子それぞれの発光層を形成する。Ｒ素子の発光層としては、ホストとして４，４’‐Ｂｉｓ（Ｎ‐ｃａｒｂａｚｏｌｅ）ｂｉｐｈｅｎｙｌ（以下、ＣＢＰと呼ぶ）と、燐光発光性化合物Ｂｉｓ［２‐（２’‐ｂｅｎｚｏｔｈｉｅｎｙｌ）ｐｙｒｉｄｉｎａｔｏ‐Ｎ，Ｃ３］（ａｃｅｔｙｌａｃｅｔｏｎａｔｏ）Ｉｒｉｄｉｕｍ（以下、Ｂｔｐ２Ｉｒ（ａｃａｃ）と呼ぶ）とを共蒸着して３０ｎｍの膜厚で発光層を形成する。Ｇ素子の発光層としては、ホストとしてｔｒｉｓ‐（８‐ｈｙｄｒｏｘｙｑｕｉｎｏｌｉｎｅ）Ａｌｕｍｉｎｕｍ（以下、Ａｌｑ３と呼ぶ）と、発光性化合物３‐（２’‐Ｂｅｎｚｏｔｈｉａｚｏｌｙｌ）‐７‐Ｎ，Ｎ‐ｄｉｅｔｈｙｌａｍｉｎｏｃｏｕｍａｒｉｎ（以下、クマリン６と呼ぶ）とを共蒸着して３０ｎｍの膜厚で発光層を形成する。Ｂ素子の発光層としては、ホストとして下記に示す化合物［ＩＩ］と発光性化合物［ＩＩＩ］とを共蒸着して３０ｎｍの膜厚で発光層を形成する。蒸着時の真空度は１×１０−４Ｐａ、成膜速度は０．２ｎｍ／ｓｅｃである。 Next, as the light emitting layer, the light emitting layers of the R element, the G element, and the B element are formed using a shadow mask. As the light-emitting layer of the R element, 4,4′-Bis (N-carbazole) biphenyl (hereinafter referred to as CBP) and phosphorescent compound Bis [2- (2′-benzothienyl) pyridinato-N, C3 are used as a host. ] (Acetylacetonato) Iridium (hereinafter referred to as Btp2Ir (acac)) is co-evaporated to form a light emitting layer with a thickness of 30 nm. As a light emitting layer of the G element, tris- (8-hydroxyquinoline) Aluminum (hereinafter referred to as Alq3) and a light emitting compound 3- (2′-Benzothiazolyl) -7-N, N-diethylaminocoumarin (hereinafter referred to as coumarin) are used. 6) is co-evaporated to form a light emitting layer with a thickness of 30 nm. As a light emitting layer of the B element, a compound [II] and a light emitting compound [III] shown below are co-deposited as a host to form a light emitting layer with a thickness of 30 nm. The degree of vacuum during vapor deposition is 1 × 10 −4 Pa, and the film formation rate is 0.2 nm / sec.
さらに、Ｒ素子、Ｇ素子、Ｂ素子に共通の電子輸送層として、１、１０‐Ｂａｔｈｏｐｈｅｎａｎｔｈｒｏｌｉｎｅ（以下、ＢＰｈｅｎと呼ぶ）を真空蒸着法にて１０ｎｍの膜厚で一括して形成する。蒸着時の真空度は１×１０−４Ｐａ、成膜速度は０．２ｎｍ／ｓｅｃである。次に、Ｒ素子、Ｇ素子、Ｂ素子に共通の電子注入層として、ＢＰｈｅｎとＣｓ２ＣＯ３とを共蒸着（重量比９０：１０）し、３０ｎｍの膜厚で一括して形成する。蒸着時の真空度は３×１０−４Ｐａ、成膜速度は０．２ｎｍ／ｓｅｃである。 Furthermore, as an electron transport layer common to the R element, the G element, and the B element, 1,10-Bathophanethroline (hereinafter referred to as BPhen) is collectively formed with a film thickness of 10 nm by a vacuum deposition method. The degree of vacuum during vapor deposition is 1 × 10 −4 Pa, and the film formation rate is 0.2 nm / sec. Next, as an electron injection layer common to the R element, G element, and B element, BPhen and Cs 2 CO 3 are co-evaporated (weight ratio 90:10) and are collectively formed with a film thickness of 30 nm. The degree of vacuum at the time of vapor deposition is 3 × 10 −4 Pa, and the film formation rate is 0.2 nm / sec.
電子注入層まで形成した基板を、真空を破ること無しにスパッタ装置に移動し、金属半透明電極１０４として、スパッタリングによりＡｇ合金を２４ｎｍの膜厚で形成する。 The substrate formed up to the electron injection layer is moved to a sputtering apparatus without breaking the vacuum, and an Ag alloy is formed to a thickness of 24 nm by sputtering as the metal translucent electrode 104.
さらに、図１２のように誘電体層１０４Ｂとして、スパッタリングによりシリカを２９０ｎｍの膜厚で形成する。 Further, as shown in FIG. 12, as the dielectric layer 104B, silica is formed to a thickness of 290 nm by sputtering.
さらに、発光装置の周辺部に吸湿剤を配置し、エッチングされたキャップガラスで封止することにより、有機ＥＬ発光装置を得る。 Furthermore, an organic EL light emitting device is obtained by disposing a hygroscopic agent in the periphery of the light emitting device and sealing with an etched cap glass.
＜実施例２＞
レジストパターンの形成までは、実施例１と同様である。
<Example 2>
The process up to the formation of the resist pattern is the same as that of Example 1.
リフトオフ加工によって、反射電極１０２表面に、図８に示すような上に凸型の周期構造３００を形成する。スパッタリングによりＡｇ合金を２０ｎｍの膜厚で形成する。ポジ型レジストの露光部分では反射電極１０２上にＡｇ合金が、ポジ型レジストの露光部分以外ではレジスト上にＡｇ合金が形成される。その後、レジストを剥離し、レジスト上のＡｇ合金ごと取り除いて、上に凸型の周期構造３００を形成する。 As shown in FIG. 8, a convex periodic structure 300 is formed on the surface of the reflective electrode 102 by lift-off processing. An Ag alloy is formed with a film thickness of 20 nm by sputtering. An Ag alloy is formed on the reflective electrode 102 in the exposed portion of the positive resist, and an Ag alloy is formed on the resist in a portion other than the exposed portion of the positive resist. Thereafter, the resist is peeled off, and the Ag alloy on the resist is removed to form a convex periodic structure 300 on the upper side.
本実施例２では、Ｒ周期構造３１０は周期３４５ｎｍ、一辺の長さ径２００ｎｍ、高さ２０ｎｍとされる。Ｇ周期構造３２０は周期２５０ｎｍ、一辺の長さ径１４０ｎｍ、高さ２０ｎｍとされる。Ｂ周期構造３３０は周期２００ｎｍ、一辺の長さ１４５ｎｍ、高さ２０ｎｍとされる。また、ＲＧＢの各素子で、１０周期ごとに周期構造３００が存在する部分と平坦な部分とが交互に並んでいる。 In Example 2, the R periodic structure 310 has a period of 345 nm, a side diameter of 200 nm, and a height of 20 nm. The G periodic structure 320 has a period of 250 nm, a side diameter of 140 nm, and a height of 20 nm. The B periodic structure 330 has a period of 200 nm, a side length of 145 nm, and a height of 20 nm. In each of the RGB elements, the portion where the periodic structure 300 exists and the flat portion are alternately arranged every 10 cycles.
次に、剥離剤によりレジストパターンを取り除く。スパッタリングにより透明導電性材料のＩＺＯを８０ｎｍの膜厚で形成して電極のパターニングをし、フォトニック結晶付きの陽極を形成する。反射電極上の周期構造３００の高さを低く抑制し、反射電極上の透明電極１０３Ｂの膜厚を厚くすることで、平坦性を改善させる。 Next, the resist pattern is removed with a release agent. A transparent conductive material IZO is formed to a thickness of 80 nm by sputtering to pattern the electrode, thereby forming an anode with a photonic crystal. Flatness is improved by suppressing the height of the periodic structure 300 on the reflective electrode to be low and increasing the thickness of the transparent electrode 103B on the reflective electrode.
さらに、酸化窒化珪素（ＳｉＮｘＯｙ）の素子分離層１１０を３２０ｎｍの膜厚で形成した後、各副画素にＥＬ発光領域となる開口部をエッチングし、フォトニック結晶を配置した陽極基板を作製する。 Further, after forming an element isolation layer 110 of silicon oxynitride (SiN x O y ) with a thickness of 320 nm, an opening serving as an EL light emitting region is etched in each subpixel, and an anode substrate on which a photonic crystal is arranged is formed. Make it.
これをイソプロピルアルコール（ＩＰＡ）で超音波洗浄し、次いで、煮沸洗浄後乾燥する。その後、ＵＶ／オゾン洗浄してからＲ、Ｇ、Ｂそれぞれの有機層１１１、１２１、１３１を真空蒸着により形成する。 This is subjected to ultrasonic cleaning with isopropyl alcohol (IPA) and then dried after boiling and drying. Then, after UV / ozone cleaning, R, G, and B organic layers 111, 121, and 131 are formed by vacuum deposition.
化合物［Ｉ］を、シャドーマスクを用いて各副画素に、Ｒホール輸送層として１５０ｎｍの膜厚、Ｇホール輸送層として９０ｎｍの膜厚、Ｂホール輸送層として４０ｎｍの膜厚で形成する。この際の真空度は１×１０−４Ｐａ、蒸着レートは、０．２ｎｍ／ｓｅｃである。発光層の形成から電子注入層の形成までは、実施例１と同様である。 Compound [I] is formed in each subpixel with a shadow mask using a shadow mask with a thickness of 150 nm as the R hole transport layer, a thickness of 90 nm as the G hole transport layer, and a thickness of 40 nm as the B hole transport layer. The degree of vacuum at this time is 1 × 10 −4 Pa, and the deposition rate is 0.2 nm / sec. The process from the formation of the light emitting layer to the formation of the electron injection layer is the same as in Example 1.
電子注入層まで形成した基板を、真空を破ること無しにスパッタ装置に移動し、金属半透明電極１０４として、スパッタリングによりＡｇ合金を２０ｎｍの膜厚で形成する。 The substrate formed up to the electron injection layer is moved to a sputtering apparatus without breaking the vacuum, and an Ag alloy is formed to a thickness of 20 nm by sputtering as the metal translucent electrode 104.
さらに、図１２のように誘電体層１０４Ｂとして、スパッタリングによりシリカを７０ｎｍの膜厚で形成する。 Further, as shown in FIG. 12, as the dielectric layer 104B, silica is formed to a thickness of 70 nm by sputtering.
さらに、発光装置の周辺部に吸湿剤を配置し、エッチングされたキャップガラスで封止することにより、有機ＥＬ発光装置を得る。 Furthermore, an organic EL light emitting device is obtained by disposing a hygroscopic agent in the periphery of the light emitting device and sealing with an etched cap glass.
＜実施例３＞
上に凸型の周期構造３００を形成するまでは、実施例２と同様である。
次に、剥離剤によりレジストパターンを取り除く。次に、スピンコートにより、ＳＯＧを３０ｎｍの膜厚で形成し平坦化する。さらに、スパッタリングにより透明導電性材料のＩＺＯを６０ｎｍの膜厚で形成して電極のパターニングをし、フォトニック結晶付きの陽極を形成する。素子分離層１１０の形成以降は、実施例２と同様である。つまり、周期構造を平坦化する平坦化層を有する構成とされている。
<Example 3>
The process until the convex periodic structure 300 is formed is the same as that of the second embodiment.
Next, the resist pattern is removed with a release agent. Next, SOG is formed with a film thickness of 30 nm by spin coating and planarized. Further, the transparent conductive material IZO is formed to a thickness of 60 nm by sputtering to pattern the electrode, thereby forming an anode with a photonic crystal. Subsequent to the formation of the element isolation layer 110 is the same as that of the second embodiment. In other words, the structure includes a planarization layer that planarizes the periodic structure.
＜実施例４＞
図１５に実施例４の有機ＥＬ発光装置の構成図を示す。ホール輸送層の形成までは、実施例１と同様である。次に、共通の３色積層型白色（Ｗ）発光層として、ＣＢＰとＢｉｓ［（４，６‐ｄｉｆｌｕｏｒｏｐｈｅｎｙｌ）ｐｙｒｉｄｉｎａｔｏ‐Ｎ，Ｃ２］（ｐｉｃｏｌｉｎａｔｏ）Ｉｒｉｄｉｕｍ（以下、ＦＩｒｐｉｃと呼ぶ）（重量比９４：６）とを共蒸着により２５ｎｍの膜厚で形成する。そして、ＣＢＰとＢｔｐ２Ｉｒ（ａｃａｃ）（重量比９２：８）とを共蒸着により２ｎｍの膜厚で形成する。さらに、ＣＢＰとＢｉｓ（２‐ｐｈｅｎｙｌｂｅｎｚｏｔｈｉｏｚｏｌａｔｏ‐Ｎ‐Ｃ２）Ｉｒｉｄｉｕｍ（ａｃｅｔｙｌａｃｅｔｏｎａｔｅ）（以下、Ｂｔ２Ｉｒ（ａｃａｃ）と呼ぶ）（重量比９２：８）とを共蒸着により２ｎｍの膜厚で形成し積層構造とする。電子輸送層の形成以降は、実施例１と同様である。
<Example 4>
FIG. 15 shows a configuration diagram of an organic EL light emitting device of Example 4. The process up to the formation of the hole transport layer is the same as in Example 1. Next, CBP and Bis [(4,6-difluorophenyl) pyridinato-N, C2] (picolinato) Iridium (hereinafter referred to as FIrpic) (weight ratio 94: as a common three-color laminated white (W) light emitting layer) 6) is formed with a film thickness of 25 nm by co-evaporation. Then, CBP and Btp2Ir (acac) (weight ratio 92: 8) are formed to a thickness of 2 nm by co-evaporation. Further, CBP and Bis (2-phenylbenzothiolato-N-C2) Iridium (aceyllacetonate) (hereinafter referred to as Bt2Ir (acac)) (weight ratio 92: 8) are formed to a thickness of 2 nm by co-evaporation. To do. After the formation of the electron transport layer, the process is the same as in Example 1.
つまり、本実施例の有機ＥＬ発光装置は各副画素にＷ有機層１７１が形成されており、白色の有機ＥＬ素子を有する構成とされている。 In other words, the organic EL light-emitting device of this example has a configuration in which the W organic layer 171 is formed in each sub-pixel and has a white organic EL element.
＜実施例５＞
レジストパターンの形成までは、実施例１と同様である。
<Example 5>
The process up to the formation of the resist pattern is the same as that of Example 1.
リフトオフ加工によって、反射電極１０２表面に、図８に示すような上に凸型の周期構造３００を形成する。スパッタリングによりＡｇ合金を３０ｎｍの膜厚で形成する。ポジ型レジストの露光部分では反射電極１０２上にＡｇ合金が、ポジ型レジストの露光部分以外ではレジスト上にＡｇ合金が形成される。その後、レジストを剥離し、レジスト上のＡｇ合金ごと取り除いて、上に凸型の周期構造３００を形成する。 As shown in FIG. 8, a convex periodic structure 300 is formed on the surface of the reflective electrode 102 by lift-off processing. An Ag alloy is formed with a thickness of 30 nm by sputtering. An Ag alloy is formed on the reflective electrode 102 in the exposed portion of the positive resist, and an Ag alloy is formed on the resist in a portion other than the exposed portion of the positive resist. Thereafter, the resist is peeled off, and the Ag alloy on the resist is removed to form a convex periodic structure 300 on the upper side.
本実施例５では、Ｒ周期構造３１０は周期３４５ｎｍ、一辺の長さ径２００ｎｍ、高さ３０ｎｍとされる。Ｇ周期構造３２０は周期２５０ｎｍ、一辺の長さ径１４０ｎｍ、高さ３０ｎｍとされる。Ｂ周期構造３３０は周期２００ｎｍ、一辺の長さ１４５ｎｍ、高さ３０ｎｍとされる。また、ＲＧＢの各素子で、１０周期ごとに周期構造３００が存在する部分と平坦な部分とが交互に並んでいる。 In Example 5, the R periodic structure 310 has a period of 345 nm, a side diameter of 200 nm, and a height of 30 nm. The G periodic structure 320 has a period of 250 nm, a side diameter of 140 nm, and a height of 30 nm. The B periodic structure 330 has a period of 200 nm, a side length of 145 nm, and a height of 30 nm. In each of the RGB elements, the portion where the periodic structure 300 exists and the flat portion are alternately arranged every 10 cycles.
次に、剥離剤によりレジストパターンを取り除く。Ａｇ合金からなる反射電極１０２と周期構造３００を、酸化やハロゲン化などの劣化から防ぐために、スパッタリングにより保護層として窒化膜ＳｉＮｘを３０ｎｍの膜厚で形成する。さらに、スパッタリングにより透明導電性材料のＩＺＯを２０ｎｍの膜厚で形成して電極のパターニングをし、フォトニック結晶付きの陽極を形成する。 Next, the resist pattern is removed with a release agent. In order to prevent the reflective electrode 102 made of an Ag alloy and the periodic structure 300 from deterioration such as oxidation and halogenation, a nitride film SiNx is formed as a protective layer by sputtering to a thickness of 30 nm. Further, the transparent conductive material IZO is formed to a thickness of 20 nm by sputtering to pattern the electrode, thereby forming an anode with a photonic crystal.
さらに、酸化窒化珪素（ＳｉＮｘＯｙ）の素子分離層１１０を３２０ｎｍの膜厚で形成した後、各副画素にＥＬ発光領域となる開口部をエッチングし、フォトニック結晶を配置した陽極基板を作製する。 Further, after forming an element isolation layer 110 of silicon oxynitride (SiN x O y ) with a thickness of 320 nm, an opening serving as an EL light emitting region is etched in each subpixel, and an anode substrate on which a photonic crystal is arranged is formed. Make it.
これをイソプロピルアルコール（ＩＰＡ）で超音波洗浄し、次いで、煮沸洗浄後乾燥する。その後、ＵＶ／オゾン洗浄してからＲ、Ｇ、Ｂそれぞれの有機層１１１、１２１、１３１を真空蒸着により形成する。 This is subjected to ultrasonic cleaning with isopropyl alcohol (IPA) and then dried after boiling and drying. Then, after UV / ozone cleaning, R, G, and B organic layers 111, 121, and 131 are formed by vacuum deposition.
化合物［Ｉ］を、シャドーマスクを用いて各副画素に、Ｒホール輸送層として１８０ｎｍの膜厚、Ｇホール輸送層として１２０ｎｍの膜厚、Ｂホール輸送層として７０ｎｍの膜厚で形成する。この際の真空度は１×１０−４Ｐａ、蒸着レートは、０．２ｎｍ／ｓｅｃである。発光層の形成以降は、実施例２と同様である。つまり、周期構造を保護する保護層を有する構成とされている。 Compound [I] is formed in each subpixel with a shadow mask using a shadow mask with a thickness of 180 nm as an R hole transport layer, a thickness of 120 nm as a G hole transport layer, and a thickness of 70 nm as a B hole transport layer. The degree of vacuum at this time is 1 × 10 −4 Pa, and the deposition rate is 0.2 nm / sec. After the formation of the light emitting layer, the process is the same as in Example 2. In other words, the protective layer for protecting the periodic structure is provided.
＜比較例１＞
反射電極１０２の形成までは、実施例１と同様である。スパッタリングによりＩＺＯを２０ｎｍの膜厚で形成して電極のパターニングをし、陽極を形成する。ホール輸送層の形成以降は、実施例１と同様である。つまり、共振器を有しており、周期構造を有さない構成である。
<Comparative Example 1>
The processes until the formation of the reflective electrode 102 are the same as those in the first embodiment. IZO is formed to a thickness of 20 nm by sputtering to pattern the electrode, thereby forming an anode. After the formation of the hole transport layer, the process is the same as in Example 1. That is, it has a resonator and does not have a periodic structure.
表１に、実施例１と比較例１におけるＲＧＢの各素子の発光強度（外部に取り出される発光スペクトルのピーク波長での強度比）の数値計算による評価値を示す。比較例１の波高強度を１とした場合、実施例１の発光強度は、ＲＧＢの全ての素子において約１．８倍となり、光取り出し効率が向上することがわかる。 Table 1 shows evaluation values by numerical calculation of the emission intensity (intensity ratio at the peak wavelength of the emission spectrum extracted outside) of each of the RGB elements in Example 1 and Comparative Example 1. When the wave height intensity of Comparative Example 1 is 1, the light emission intensity of Example 1 is about 1.8 times in all the RGB elements, indicating that the light extraction efficiency is improved.
１００ 基板
１０１ 有機層
１０２ 反射電極
１０３ 透明電極
１０３Ｂ 反射電極上の透明電極
１０４ 金属半透明電極
１０４Ｂ 誘電体層
１０５ 発光層
１０６ ホール輸送層
１０７ 電子輸送層
１０８ ホール注入層
１０９ 電子注入層
１１０ 素子分離層
１１１ Ｒ有機層
１１５ Ｒ発光層
１２１ Ｇ有機層
１２５ Ｇ発光層
１３１ Ｂ有機層
１３５ Ｂ発光層
１７１ Ｗ有機層
２０１ 発光点
２０２ 伝播光
２０３ 導波光
２０４ 回折光
３００ 周期構造
３０１ 光導波路
３０２ ＥＬ発光領域
３１０ Ｒ周期構造
３１１ Ｒ光導波路
３２０ Ｇ周期構造
３２１ Ｇ光導波路
３３０ Ｂ周期構造
３３１ Ｂ光導波路
DESCRIPTION OF SYMBOLS 100 Substrate 101 Organic layer 102 Reflective electrode 103 Transparent electrode 103B Transparent electrode on reflective electrode 104 Metal translucent electrode 104B Dielectric layer 105 Light emitting layer 106 Hole transport layer 107 Electron transport layer 108 Hole injection layer 109 Electron injection layer 110 Element isolation layer 111 R organic layer 115 R light emitting layer 121 G organic layer 125 G light emitting layer 131 B organic layer 135 B light emitting layer 171 W organic layer 201 light emitting point 202 propagating light 203 waveguided light 204 diffracted light 300 periodic structure 301 optical waveguide 302 EL light emitting region 310 R periodic structure 311 R optical waveguide 320 G periodic structure 321 G optical waveguide 330 B periodic structure 331 B optical waveguide
Claims (12)
前記発光素子は、前記基板の上に形成されている反射電極である第１電極と、前記第１電極の上に形成されている発光層と、前記発光層の上に形成されている第２電極と、を有し、
前記発光層で発光する光を、前記第１電極にある第１反射面と、前記第２電極にある第２反射面との間で共振させる共振器を有する発光装置において、
前記発光層で発生し前記第１反射面と前記第２反射面との間を前記発光素子の面内方向に導波する光を前記発光素子の外に取り出す周期構造が、前記第１反射面に形成されており、
前記周期構造は、前記発光素子の発光領域内に部分的に形成されており、
前記基板垂直方向に沿った前記周期構造の高さｈが、外部に取り出される光のスペクトルのピーク波長λ、前記第１反射面と前記第２反射面との間の平均屈折率ｎに対して、
を満たしていることを特徴とする発光装置。 A substrate and a plurality of light emitting elements formed on the substrate;
The light emitting element includes a first electrode that is a reflective electrode formed on the substrate, a light emitting layer formed on the first electrode, and a second electrode formed on the light emitting layer. An electrode, and
The light emitted from the light emitting layer, and a front Symbol first reflecting surface in the first electrodes, the light-emitting device having a resonator which resonates with the previous SL second reflecting surface in the second electrodes,
A periodic structure for taking out the light generated in the light emitting layer and guided between the first reflecting surface and the second reflecting surface in the in-plane direction of the light emitting element to the outside of the light emitting element is the first reflecting surface. Is formed,
The periodic structure is partially formed in a light emitting region of the light emitting element,
The height h of the periodic structure along the vertical direction of the substrate is relative to the peak wavelength λ of the spectrum of light extracted outside, and the average refractive index n between the first reflecting surface and the second reflecting surface. ,
A light emitting device characterized by satisfying
各発光素子における前記周期構造の高さは同じであり、いずれも６０ｎｍより低いことを特徴とする請求項１又は請求項２に記載の発光装置。 The plurality of light emitting elements include the light emitting element emitting red light, the light emitting element emitting green light, and the light emitting element emitting blue light.
3. The light emitting device according to claim 1, wherein heights of the periodic structures in the respective light emitting elements are the same, and all are lower than 60 nm.
前記周期構造の周期は、前記赤色発光の発光素子が最も長く、前記青色発光の発光素子が最も短いことを特徴とする請求項１乃至請求項５のいずれか１項に記載の発光装置。 The plurality of light emitting elements include the light emitting element emitting red light, the light emitting element emitting green light, and the light emitting element emitting blue light.
Period of the periodic structure, the red light-emitting element is the longest, the light emitting device according to any one of claims 1 to 5 the light-emitting element of the blue emission and wherein the shortest.
前記発光層は、前記平坦化層の上に形成されていることを特徴とする請求項１乃至請求項７のいずれか１項に記載の発光装置。 A planarizing layer for planarizing the surface of the periodic structure on the periodic structure;
The EML emitting device according to any one of claims 1 to 7, characterized in that it is formed on the planarization layer.
前記発光層で発光する光は、前記第２電極から外部に取り出されることを特徴とする請求項１乃至請求項１０のいずれか１項に記載の発光装置。 The second electrode is a light transmitting electrode or a metal translucent electrode;
The light emitted from the light emitting layer, the light emitting device according to any one of claims 1 to 1 0, characterized in that extracted outside from the second electrode.
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